The German patent application DE 10 2006 059 190 A1 discloses an apparatus for the inspection of a wafer. For the inspection of the wafer at least one illumination system is provided, which emits a respective illumination light beam along a respective illumination path onto the surface of a wafer. A detection system defines a detection path, wherein the detection system exhibits a defined spectral sensitivity and collects data from at least one illuminated region on the surface of the wafer; the illuminated region is moving along a scan direction. The moving region can be evaluated within plural spectral ranges. The at least one illumination system is a continuous light source.
The German patent application DE 10 2007 002 711 A1 discloses an apparatus for the inspection of the surface of a wafer. The apparatus comprises at least one top-light illumination system for illuminating the surface of the wafer with a first and a second type of illumination. The first and the second type of illumination in particular are a bright field illumination and/or a dark field illumination. Furthermore an image capture device is provided to capture an image of the illuminated region. Moreover a system for storing intensity values is provided, in order to determine the colour of an optimized illumination of each type of top-light illumination.
The German patent DE 10 2004 029 014 B4 relates to a method and an apparatus for the inspection of a wafer. The method and the apparatus in particular are provided for the detection of macro defects, like for instance errors in exposure, wherein at least a part of the wafer surface is illuminated by a source of radiation. An image of this surface is recorded with a camera and is the basis for the inspection of the surface of the wafer. In order to conduct the detection of defects at optimal image contrast, it is proposed to illuminate the surface of the wafer telecentrically with a small illumination aperture. Therefore the source of radiation is provided with a corresponding system of lenses.
The German patent DE 10 2005 038 034 B3 shows an apparatus designed for bright field inspection with orthogonally incident light. The illumination system illuminates the surface of the wafer in the inspected area orthogonally from above with three narrow spectra, provided in the spectral ranges of red, green, and blue. The capture device captures the image formed by the light reflected from the inspected area orthogonally from above through the beam splitter. Due to the bright field inspection setup the light directed onto the inspected area by the illumination system interferes with transparent thin layers in the inspected area. Thus by interference effects fluctuations of layer thickness as well as of optical thickness can be reduced.
The US patent application US 2008/0007726 discloses an inspection system for wafers characterized by a high throughput. Light from a bright field illumination system is directed onto a review camera by a movable mirror. The dark field illumination system comprises a laser with an adjustable angle. The scattered light is detected with a TDI-sensor. The difference with the present invention is that the dark field illumination is done with a laser. For each type of illumination moreover a different detector is provided. There is no essentially identical capture of bright field images and dark field images of the surface of the wafer.
In the US patent application US 2006/0146319 an apparatus is disclosed for recording plural bright field images and plural dark field images from one and the same region on the surface of a wafer. In order to obtain information from the dark field illumination on the surface of the wafer, plural lasers are provided which differ in their frequencies. For the bright field illumination also plural light sources are provided, which also differ in frequency. For recording the different types of information, plural detectors are provided. The detectors receive the laser light scattered from the surface of the wafer through a spatial filter. The light from the bright field illumination system reaches the detector or detectors, respectively, which are TDI sensors, via a beam splitter. It is also possible to use a camera which is an RGB-camera provided with three CCD chips.
The Japanese patent application JP 2007-183283 shows two cameras, one camera being located in the bright field setup. With a second camera scattered light from the surface of the wafer can be recorded.
According to the Japanese patent application JP 2003-017536 two one-dimensional CCD cameras are disclosed, which record scattered light from two lasers. The light from the lasers impinges on the surface of the wafer with an angle. The intensity of the lasers can be monitored and controlled accordingly.
The German patent application DE 103 59 723 A1 discloses at least one microscopic top-light illumination system for directing a pulsed illumination beam onto a surface of a wafer and illuminating an area on the surface of the wafer. Furthermore an image capture device is provided in order to capture an image of the respective illuminated area of the surface of the wafer. Therein the illuminated area is smaller than the surface of the wafer. Furthermore a system is provided for detecting intensity fluctuations of the light pulses of the top-light illumination system and for controlling them accordingly.
In the German patent application DE 103 59 722 A1 defects on a wafer can be detected with bright field and or dark field illumination. The radiation incident on the wafer has a substantial effect on the reliability of the measurement results. In order to improve the reliability of the measurement results the wafer is illuminated with an illumination system wherein essentially its brightness and frequency are set with reference to previously stored nominal illumination values.
The German patent application DE 198 56 219 A1 discloses a fibre optical output coupling for monitoring the light intensity in a fibre optical cable. The outer covering layer is removed and the underlying cladding is roughened, so that light in the cladding is radiated out. A photodetector is positioned close to the polished surface and optically insulated from other light sources. The signal generated by the photodetector is an indication of the light intensity in the fibre. Control or adjustment, respectively, of the light intensity of the light sources is not discussed in this document.
The German patent application DE 103 52 590 A1 discloses a method for producing an optical fibre with an output coupling point for scattered light for monitoring the power of light passed through the optical fibre. The optical fibre comprises a core with a first refractive index, and a cladding surrounding the core with a second refractive index. The second refractive index is smaller than the first refractive index. A section of the optical fibre is essentially straight in the region of the output coupling point. The optical fibre is electrothermically treated at a location within the essentially straight section in such a way that in the boundary region of core and cladding a partial mixture of core material and cladding material is generated and thus scattering centres are produced, turning the treated location into the output coupling point.
The German patent application DE 103 30 003 relates to an apparatus for the inspection of a wafer. The apparatus comprises at least one illumination system for directing an illumination beam onto a surface of the wafer. An image capture device is provided for capturing an image of an illuminated area on the surface of the wafer in a plurality of spectral ranges. A colour changing device is provided for changing the colour of the illumination beam or of the reflected beam. The wafer inspection apparatus is characterised in that the colour changing device is designed in such a way that the colour spectrum of the illumination beam or of the image recorded from the surface of the wafer is adaptable to the spectral sensitivity of the image capture device.
U.S. Pat. No. 6,847,443 discloses a triple filter in the illumination path. In this way the wafer can be illuminated with three selectable wave lengths or wave length intervals, respectively. The disadvantage is that the light from the wafer reaches the camera provided for detection directly and without additional filtering.
The German patent application DE 103 30 506 A1 discloses an apparatus for the inspection of wafers. A table which is movable in two mutually orthogonal directions is supported on air bearings. The wafer to be inspected can be moved along a meander-like path with the table, in order to create a plurality of image windows, out of which the entire surface of the wafer can be composed.
The German patent application DE 103 51 848 A1 discloses a system for the detection of macro defects. The system is surrounded by a casing. The individual elements of the system are located in a first, a second, and a third section. The second section comprises a measurement table movable in X-coordinate direction and in Y-coordinate direction. Furthermore air guides are provided within the casing of the system, so that a flow of air can be produced over the wafer placed on the measurement table; the flow of air is essentially parallel to the wafer.
The German patent DE 103 30 005 B4 discloses an apparatus for the inspection of a wafer. The apparatus comprises at least one top light illumination system, which emits light into an illumination path, which encloses an angle with the surface of the wafer. Furthermore an image capture device is provided for recording an image of the surface in the dark field setup. Furthermore at least a dimmer is provided, which directs the light beam onto the surface of the wafer.
The German patent DE 103 30 006 B4 also discloses an apparatus for the inspection of a wafer. The apparatus comprises two light sources in a top light setup, which emit light onto the surface of the wafer in an optical path. The light from the light sources impinges onto the surface of the wafer under an angle. An image capture device records a corresponding image of the respectively illuminated image window. The two light sources are arranged in such a way that the illumination path of the light sources is orthogonal to the linear structures of the dies on the wafer.
The US patent application US 2003/0086083 A1 discloses a positioning system for a metrology apparatus. A beam splitter splits the light from the object to be measured into a first path and a second path. One path is provided for high magnification and the other path is provided for low magnification.